WPF

private void PopulateContactsListBox()
{
   listBoxContacts.Items.Clear();
   listBoxContacts.ItemsSource = contactClient.GetContacts();
}

 class MElement :UIElement, INotifyPropertyChanged
    {
 public static readonly DependencyProperty PositionXProperty = DependencyProperty.Register(
            "PositionX",
            typeof(int),
            typeof(MElement),
            new FrameworkPropertyMetadata(
            new PropertyChangedCallback(OnPositionChanged))
            );

        public int PositionX
        {
            get { return (int)this.GetValue(PositionXProperty); }
            set { this.SetValue(PositionXProperty, value); }
        }

public event PropertyChangedEventHandler PropertyChanged;

private static void OnPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (PropertyChanged !=null) //this won't work, which makes sense - but doens' allow to be declared static
               {
                  // fire PropertyChanged event
               }
        }
}